41 81 ME 4563 Fall ’05 Dr. S. Haran Casting & Hot Rolling Casting & Hot Rolling – – a schematic a schematic 82 ME 4563 Fall ’05 Dr. S. Haran Slab Hot mill Roller table Warm mill Take-up roll Hot Rolling Mill Design Hot Rolling Mill Design • • Basically the same as cold mills, but designed for Basically the same as cold mills, but designed for higher temperatures and are reversible higher temperatures and are reversible • • Typically have edging rolls to control thickness Typically have edging rolls to control thickness • • Often have a warm mill at the end Often have a warm mill at the end 42 83 ME 4563 Fall ’05 Dr. S. Haran Hot Rolling Mill Design Hot Rolling Mill Design • • Basically the same as cold mills, but designed for Basically the same as cold mills, but designed for higher temperatures and are reversible higher temperatures and are reversible • • Typically have edging rolls to control thickness Typically have edging rolls to control thickness • • Often have a warm mill at the end Often have a warm mill at the end Slab Hot mill Roller table Warm mill Take-up roll 84 ME 4563 Fall ’05 Dr. S. Haran Hot Rolling Process Hot Rolling Process - - Example Example • • Start with 12in. thick slab, 20 feet long Start with 12in. thick slab, 20 feet long • • Hot mill converts to 2 in thick slab, 120 feet long with Hot mill converts to 2 in thick slab, 120 feet long with 11 passes (six forward and 5 reverse) 11 passes (six forward and 5 reverse) • • Front end sheared off to eliminate alligatoring Front end sheared off to eliminate alligatoring • • Warm mill converts this to Warm mill converts this to roll roll of sheet 0.25 in thick, of sheet 0.25 in thick, 960 feet long 960 feet long • • Rolls more easily handled by overhead cranes to Rolls more easily handled by overhead cranes to transport it to cold mills than 1000 ft long slabs transport it to cold mills than 1000 ft long slabs 43 85 ME 4563 Fall ’05 Dr. S. Haran Overall Process for Sheet and Plate Overall Process for Sheet and Plate • • Cast ingot Cast ingot • • Scalp (not always) Scalp (not always) • • Reheat and homogenize (uniform) Reheat and homogenize (uniform) • • Hot roll in reversing mill to ~1 Hot roll in reversing mill to ~1 - - 2 in thick 2 in thick • • Cut off ends (alligators) Cut off ends (alligators) • • Warm roll to 0.1 Warm roll to 0.1 - - 2 in thick 2 in thick • • Heat treat to recrystallize (sometimes) Heat treat to recrystallize (sometimes) • • Cool Cool • • Cold roll to finish thickness Cold roll to finish thickness • • Heat treat (where appropriate) Heat treat (where appropriate) • • Results in material which must be further worked Results in material which must be further worked 86 ME 4563 Fall ’05 Dr. S. Haran Hot Rolling Hot Rolling 44 87 ME 4563 Fall ’05 Dr. S. Haran Hot Rolling Hot Rolling 88 ME 4563 Fall ’05 Dr. S. Haran Rolling Rolling Mill Mill Hot Rolling Hot Rolling 45 89 ME 4563 Fall ’05 Dr. S. Haran Hot Rolling Hot Rolling Closer Look Closer Look Hot Rolling Hot Rolling 90 ME 4563 Fall ’05 Dr. S. Haran Continuous Continuous Steel Steel Casting Line Casting Line rolling out rolling out billets billets Hot Rolling Hot Rolling 46 91 ME 4563 Fall ’05 Dr. S. Haran Continuous Continuous Rolling of Rolling of Billets Billets Hot Rolling Hot Rolling 92 ME 4563 Fall ’05 Dr. S. Haran Steel Billets Steel Billets Steel Slabs (from slab caster) Steel Slabs (from slab caster) Billets Billets Casting Casting Hot Rolling Hot Rolling 47 93 ME 4563 Fall ’05 Dr. S. Haran Hot rolled strips Hot rolled strips being coiled being coiled Hot Rolling Hot Rolling 94 ME 4563 Fall ’05 Dr. S. Haran Rolling of Rolling of Rails Rails Hot Rolling Hot Rolling 48 95 ME 4563 Fall ’05 Dr. S. Haran Hot Cutting Hot Cutting the rolled the rolled Rails Rails Hot Rolling Hot Rolling 96 ME 4563 Fall ’05 Dr. S. Haran Section of the Section of the Mill where Mill where rolling is rolling is taking place taking place Hot Rolling Hot Rolling 49 97 ME 4563 Fall ’05 Dr. S. Haran Profiled color Profiled color - - coated steel coated steel sheets sheets U U - - section long bars section long bars Rolling Rolling – – Further Processing Further Processing 98 ME 4563 Fall ’05 Dr. S. Haran Wire rods in Wire rods in a coil a coil U U - - section long bars section long bars Rolling Rolling – – Further Processing Further Processing 50 99 ME 4563 Fall ’05 Dr. S. Haran Cold Rolling Cold Rolling 100 ME 4563 Fall ’05 Dr. S. Haran   Hot rolled coil is commonly cold rolled (also known as cold Hot rolled coil is commonly cold rolled (also known as cold reduced). reduced).   The strip is first de The strip is first de - - coiled (uncoiled) and then passes through a coiled (uncoiled) and then passes through a series of rolling mill stands which apply pressure to the strip series of rolling mill stands which apply pressure to the strip and and progressively reduce its thickness progressively reduce its thickness - - down to as low as 0.15 mm. down to as low as 0.15 mm.   The strip is then recoiled. The strip is then recoiled.   Cold rolling processes are also used to improve the surface Cold rolling processes are also used to improve the surface quality of the steel. quality of the steel.   Cold rolling also has the effect of hardening steel, so cold Cold rolling also has the effect of hardening steel, so cold reduced strip is subsequently annealed: a process of very reduced strip is subsequently annealed: a process of very carefully controlled heating and cooling to soften it carefully controlled heating and cooling to soften it Cold Rolling Cold Rolling . which must be further worked 86 ME 456 3 Fall ’ 05 Dr. S. Haran Hot Rolling Hot Rolling 44 87 ME 456 3 Fall ’ 05 Dr. S. Haran Hot Rolling Hot Rolling 88 ME 456 3 Fall ’ 05 Dr. S. Haran Rolling Rolling. Mill Mill Hot Rolling Hot Rolling 45 89 ME 456 3 Fall ’ 05 Dr. S. Haran Hot Rolling Hot Rolling Closer Look Closer Look Hot Rolling Hot Rolling 90 ME 456 3 Fall ’ 05 Dr. S. Haran Continuous Continuous. Rails Rails Hot Rolling Hot Rolling 48 95 ME 456 3 Fall ’ 05 Dr. S. Haran Hot Cutting Hot Cutting the rolled the rolled Rails Rails Hot Rolling Hot Rolling 96 ME 456 3 Fall ’ 05 Dr. S. Haran Section of the